Electrical apparatus



Dec. 18, 1956 A. o. GROOMS ELECTRICAL APPARA'IVUS Filed Oct. 10, 1951 INVENTOR.

United States Patent ELECTRICAL APPARATUS Albert O. Grooms, Dayton, Ohio, assignor to General Motors Corporation, Dayton, Ohio, a corporation of Delaware Application October 10, 1951, Serial No. 250,693 2 Claims. (Cl. 200-83) This invention relates to electrical apparatus and more particularly to temperature and/or pressure controls such as may be used for refrigerating applications as well as a similar control application.

It is an object of my invention to provide a simple control for a refrigerating apparatus operating on a defrosting cycle.

It is another object of my invention to provide a control wherein the cut-off temperature may be varied without affecting the cut-on temperature.

It is another object of my invention to provide a control having a wide temperature differential so that it will be suitable for defrosting applications.

It is a further object of my invention to increase the spring loading on a toggle linkage in a minimum of space.

It is a still further object of my invention to adapt my improved control to applications other than those similar to defrosting wherein it is desirable to adjust both the cut-off and cut-on temperatures.

Further objects of my invention will be apparent from the following description, reference being had' to the accompanying drawings wherein preferred forms of the invention are clearly shown.

In the drawings:

Fig. 1 is a plan view of a refrigerator control with the casing cover shown in section;

Fig. 2 is a sectional view taken along lines 22 of I Fig. 1;

Fig. 3 is a sectional view taken along the lines 3--3 of Fig. 1; and

Fig. 4 is a partial plan view of the central portion of Fig. 1 showing a modified form of my invention.

Referring now to the drawings there is shown a U-shaped metal frame 20 which has a terminal member 22 of electrical insulating material connecting the two legs of the frame. A U-shaped cover 21 clips onto the frame 20. The terminal member 22 is provided with two terminal posts 24 and 26 which extend through the terminal member. The inner end of the terminal post 26 has connected thereto a bent leaf spring contact carrying member 28 which carries the movable contact 30. The adjustable terminal post 24 carries the stationary contact 32 which is electrically insulated from the movable contact 30 excepting when the contacts are in closed position. The terminal post 24 is connected to a supply conductor 34 while the terminal post 26 is connected to a motor 36 which may be used to drive the compressor of a refrigerating system. While the switch is shown controlling a refrigerating system, the control may be used for controlling other systems.

The lower end of the frame 20 has the lower end of the flexible metal bellows 38 connected thereto. This bellows 38 is connected by capillary tube 40 to a bulb portion, not shown, which, for example, may be fastened in metal to metal contact with the evaporator of a refrigerating system. Fastened to the closed upper end of the bellows 38 is a metal follower 48 provided at its lower end with a flange which may be soldered or Patented Dec. 1 8, 1956 2 welded to the upper closed end of the bellows 38. This follower 48 is connected at its upper end by means of a rivet 49 to an insulated extension 50 provided with a slot 52 which receives an intermediate portion of the leaf spring member 28. The lower-end of the insulated-extension 50 has a slot 53 which receives a projection 54 struck out of the follower48. 1

On either side of the extension 50' the-follower 48 is provided with V-shaped notches which receive the inner knife edges of the triangular shaped toggle links 56 and 58. The outer knife edge of the toggle link 58 bears upon a notch in a bearing member 60 which member is adapted for horizontaladjustment by means of a threaded screw 62. The outer end of the togglelink 56 isreceived in a notch in the inner face of a leaf spring64. i

.The leaf spring 64 has a tongue 68*at its lower end which extends through an opening in the bottom of the frame 20. This leaf spring 64 is provided with a vertical adjustment consisting of a threaded screw 70 acting against a coil spring 72 which bears upon the lower edge of the leaf spring. The upper end of the leaf spring is formed into an inverted U-shape and is provided with pads 74 and 76 which slidably engage the inner face of the frame 20. A flange 78 is struck out from the upper end of the leaf spring and is slidably received in a vertical slot 80 in the frame 20.

A shaft 82 extends across the frame 20 and is journaled in opposed openings in the legs of the frame. This shaft also extends through an enlarged opening formed in the leaf spring 64 and through a slot 47 formed in the follower'48. A control knob 84 and a cam 86 are splined to the shaft 82. The cam 86 engages the closed upper end of the bellows 38 and is provided with lobe 87. The cam has a continuous rise in a counterclockwise direction as viewed in Fig. 2, the rise beginning and ending with the lobe 87. A wide U-shaped clip 88 on the shaft 82 serves as a spacer to prevent longitudinal movement of the cam 86 in one direction while a stepped up shoulder on the shaft prevents longitudinal movement of the cam in the other direction. A C-shaped retaining conical spring washer 90 engages a groove in the shaft 82 and in conjunction with the shoulder formed by the splined end portion of the shaft serves to prevent horizontal movement of the shaft.

A threaded member 92 is provided to allow vertical adjustment of the bellows 38. A vertically adjustable stop 94 is threaded in a boss 95 on the terminal member 22. The stop 94 is adapted to engage a bent over flange 96 formed on the follower 48.

'In operation it can readily be seen that the follower 48 has an upper limit of movement on one side of toggle dead center which is determined by the position of the cam 86, and a lower limit of movement on the other 'side of toggle dead center which is determined by the location of the stop 94. It may be noted here that the upper limit of the follower 48 is adjustable through the counterclockwise rise in the cam and it should be understood that the lobe 87 functions solely as a positive cut-off to prevent a possible cut-on .or switch closing movement of the follower. The cam 86 thereby serves as an adjustment for the lower end of the temperature differential and, in a typical example, may be utilized to vary the cut-off temperature between minus 5 and plus 1 degrees Fahrenheit while the stop .94 will be pre-set in defrosting applications to effect a constant desired cuton temperature, for example, 36 degrees Fahrenheit.

The temperature differential can also be expanded or contracted by changing the horizontal loading on the toggle links 56 and 58 through the bearing member 60. If the toggle links are in a common plane when the follower is at one of its limits of movement, adjustment of the bearingmem'ber will affect only one end of the temperature differential. However, both ends of the temperature differential will be affected if the toggle links are in-a common plane When'the follower is intermedi-ateits range of; movement. The temperature eontro'lsused'in defrosting apparatus necessarily require a wide temperature difierential and it can be seen that this is accomplished in this construc-tionbecause of the increasedload; ing of the toggle made possible by theinverrted U-shaped end construction of the leaf spring 64, in combination with a togglepassing through dead center position. 'A'dj-ustment of the leaf spring '64 in a vertical direction will affect the temperature differentialand will also shift the range, while vertical adjustment of the bellows 38, by means of the threaded member 92, will affect the range due to the. spring action" ofthe bellows. Vertical ad; jus-tment of the bellows is utilized to adjust the control for operation at various altitudes. The terminal post 24 is made vertically adjustable so that a desired contact pressure may be obtained.

Adjustment of the control so that it may subsequently exhibit the desired characteristics when controlled by 7 What is claimed is as follows: 1

l. A control arrangement comprising a suppoit, a reciprocal actuator mounted upon said support, switch means connected to and operated by said actuator, a spring-loaded toggle connecting said actuator and said support, a first cam movably mounted on said support to adjustably limit actuator movement in one direction, a second cam movably mounted on said support to adjustably limit actuator movement in the other direction, andacontrohk'no'boperably connected to both cams for simultaneous operation of said cams.

2. A control arrangement comprising a support, an actuator mounted upon said support, and an on-o'ff switch operable with said actuator, a toggle connecting said actuator and said shpp'ofi, aleaf'sp'ring laterally shiftable with respect to said actuator and operably connected to the toggle to impart a column load on said toggle, a first cam movably mounted on said support, said actuator the control knob 84 is normally accomplished by completing the aforementioned adjustments before delivery to the user. Thus, it canbe seenthat in normal operation' there is only one active adjustment, namely, an ad just ment of the lower end of the temperature differential to the desired cut-off temperature. V

An adaptation of my invention suitable for control uses wherein it is desirable to vary thecut-on as well as the cut-off temperature is illustrated in Fig. '4. The control shown in Fig. -4 is-identical with the previously described control with the exception of an additional cam 8 also spliried on-the knob shaft 82 and having a reverse or clockwise i'ise with respect toca'm 86 and engagingthe now extendedprojection 54 on the follower 48 to limit the downward motion of the follower, thereby varying the cut-on temperature concurrentlywith variations in the cut-off temperature effected by the cam 86. It is obvious that in this modification stop 94is no longer necessary and it has therefore been omitted.

While the embodiments of the invention as herein dis: closed constitute preferred forms it is to be understood that other forms might be adopted as may come within the scope of the claims which follow.

having a portionmovable into contact with said cam to limit actuatorr'novement in the'switch opening direction, a second cam movably mounted on said support, said actuator having a portion movable into contact with said second cam to adjustably limit actuator movement in the switch closing direction, a control knob operably connected to both cams for common operation of said first and second cams, said control knob functioning only to adjust said cams, adjusting means connecting said spring and said support and adapted to shift said spring; and means independently operable of said adjusting means for varying the columnloading of said toggle.

flnerer'emes Citedin the file of this patent I UNITED STATES PATENTS f8s'7,qs7 oeissinger May 12, s 439,231 Erickson Dec. 19, 1922 1,911,530 Raisch et a1 May 30, 1933 2,061,270 anson Nov. 17,1936 ,2,35:LQ'381 Grooms June 13, 1944 2,479,047 Lang Aug. 16', 1949 2,550,792 Path May 1', 1951 2,586,506 Bixler Feb. 19, 1-952 

